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Dec. 4, 1962 H. EBERT ETAL 3,067,006 PROCESS AND APPARATUS FOR THE MANUFACTURE OF ANHYDROUS MAGNESIUM CHLORIDE WHICH IS SUBSTANTIALLY FREE FROM MAGNESIUM OXIDE Filed May a, 1960 I~ . . /NVEN7'G/PS HANS EBER T, FRIEDBERT RITTER, ERNST HARMSEN, KURT GRAPENTIN BY ' THEIR ATTORNEY A United States Patent-O?ice 2 1 3,057,006 PROCMS AND APPARATUS FOR THE MANUFAC TURE 0F ANHYDROUS MAGNESIUM CHLO RIDE WHI'JH IS SUBSTANTIALLY FREE FROM MAGNESIUM OXIDE Hans Ebert, Knapsaclr, near Koln, Friedbert Ritter, Busch hot, near Konigswinter (Rhine), Ernst I-Iarmsen, Bruhl (Rhine), and Kurt Grapentin, Koln-Zollstock, Ger many, assignors to Knapsack-Griesheim Alrtiengesell schaft, Knapsack, near Koln, Germany, a corporation of Germany Filed May 3, 1960, Ser. No. 26,466 Claims priority, application Germany May 5, 1959 4 Claims. (Cl. 23--91) The present invention is concerned with a process for the manufacture'of anhydrous magnesium chloride which is substantially free from magnesium oxide by chlorinat ing a salt which essentially consists of magnesium chlo— 31,057,006 Patented Dec. 4, 1962 processes involve the aforesaid disadvantages. Further ditiiculties arise during the admission of the required heat energy. The ?neness of the powder implies an extremely great hygroscopicity and losses of substance since the ?ne particles are entrained by a moving gas atmosphere. It is therefore necessary that the salt powder dried by atomization is melted without coming into contact with the outer atmosphere and the magnesium oxide contained in the melt is then chlorinated. When the salt powder is 10 melted, it is found that the water in the powder substan~ tially undergoes reaction with magnesium chloride, hydro gen chloride being evolved. The hydrogen chloride evolved entrains a part of the powder to be introduced so that losses of substance in the order of 10-30% cannot be avoided. The process of this invention is carried out as follows with the use of an apparatus as shown diagrammatically (longitudinal section) in the accompanying drawing. The salt is continuously introduced via charging device ride and contains about 1—5% by weight water and about 1 into, for example, an electrically heated melting bath 2 2—6% by weight magnesium oxide. The salt is intro which consists of molten magnesium chloride and is her— duced into a melt of magnesium chloride which travels through a heated chlorination device in which the ?nely metically closed with respect to the outside. In order to avoid that magnesium oxide contained in the magnesium distributed melt trickling down through carbon material chloride deposits and in order to fairly rapidly melt the is chlorinated with the aid of chlorine, phosgene, a mix~ ture of carbon monoxide and chlorine, a chlorinated hy 25 powder and to achieve a rapid heat exchange between the powder introduced and the melt, the latter is vigorously, drocarbon or hydrogen chloride, the hydrogen chloride agitated by means of stirrer 3. The melt container is evolved by hydrolysis when the salt is melted being used equipped with an over?ow 5 in order to uniformly intro; in the chlorination. The salt used as starting material duce the melt into chlorinator 4, i.e. into a column of lump may be obtained, for example, by atomization drying or in coal which is electrically heated by means of electrodes another appropriate manner. The invention is also con cerned with an apparatus suitable for use in the manufac ltl. ture of magnesium chloride. It is known that aqueous magnesium chloride solutions and magnesium chloride hydrates can be dried by atomiza prevents unmolten powder from being entrained into over-v tion so as to be converted into products of low magnesium melt trickling down and the magnesium oxide it contains oxide and water content. By this special method of dry ing, the hydrolysis can be substantially suppressed with out a special atmosphere, for example of hydrogen chlo ride, being required. The powder obtained by atomiza Over?ow 5 is series-connected to an apron 6 which flow 5 to there give rise to obstructions. Chlorine is in troduced through inlet 9 into chlorinator 4i in which the are chlorinated in counter-current. In order to avoid local cooling in chlorinator 4 at the level of chlorine inlet 9, the chlorine is pro-heated to the temperature which pre vails in said chlorinator. The carbon material, which is consumed during the chlorination, can be supplied con? tion drying has very ?ne grains which are substantially be tinuously to chlorinator 4 through inlet opening 11 and low 15 microns. Depending on the quality of the powder through the opening of over?ow 5 or through another ori-' used, a melt containing about 5-15% MgG is obtained. ?ce. It is advantageous to introduce the melt containing In a known process, magnesium is produced by sub jecting magnesium chloride to electrolysis. In this proc~ magnesium oxide into the chlorinator from a central place ess, the melt containing magnesium oxide is directly intro 45 through one or more over?ows in order to ensure that thev melt on trickling down is fairly well distributed on the duced into the apparatus used to carry out the electrolysis. lump coal. The absolutely anhydrous melt of which the‘: It is, however, more advantageous especially from an eco oxide content amounts to at most 0.l—0.2% magnesium nomical point of view to use in the electrolytic bath mag oxide is collected in the lower part of chlorinator 4. It nesium chloride which is completely free from water and oxide. 50 may be removed in discontinuous manner or, and this is The magnesium oxide contained in magnesium chloride more advantageous from an economical point of view, in continuous manner through outlet 7. I can be chlorinated and the residual water eliminated in the solid state by treating the salt powder, which contains about 1-5% H20 and 2—6% MgO, at a raised temperature but below its melting point, for example with hydrogen chloride, chlorine and carbon, phosgene, a mixture of car bon monoxide and chlorine or a chlorinated hydrocarbon. This process needs great amounts of chlorine and in volves considerable losses of substance due to the ?neness The hydrogen chloride which evolves when the salt is melted is introduced together with the melt through over ?ow 5 into chlorinator 4 and is removed through oil-gas outlet 12 together with the off-gas emanating from the chlorinator. .The o?-gas consists of carbon monoxide, carbon dioxide and a little unreacted chlorine in excess.‘ The hydrogen chloride may be recovered from the oil-gas of the salt powder. Moreover, the reaction of, for exam— 60 and re-introduced together with chlorine through chlo rine inlet 9 into the chlorinator and used for chlorinating ple, magnesium oxide and hydrogen chloride proceeds the salt melt in counter-current. very reluctantly. Alternatively, the hydrogen chloride may be used for‘ It would therefore be more advantageous in the atomi chlorination in that the off-gases of chlorinator 4 are re zation drying to dehydrate up to one hydrate of magnesi moved through short outlet pipe 8. In this manner, the um chloride with 1 or 2 mols water of hydration, whereby hydrogen chloride which evolves when the salt is melted practically no magnesium oxide is formed and then to de is conducted in co-current with the melt in the upper part hydrate said hydrate under a hydrogen chloride atmos of chlorinator 4, whereby the magnesium oxide contained phere. The dehydration may take place in a shelved in said melt is partially chlorinated. The residual mag-v drier, a rotary kiln, a ?uidized bed or by causing the pow nesium oxide is chlorinated in the lower part of chlori der in ?nely divided form to trickle down in a tower in 70 nator 4 by the chlorine flowing in counter-current. In counter-current to hydrogen chloride gas, but all these this embodiment of the invention, a part of the chlorine is 3,067,006 3 A ing device 1 through which the salt mixture to be chlori nated is supplied, a stirrer 3, a central over?ow 5, an apron 6 disposed between the melting bath 2 and over?ow 5, a lower outlet 7, gas inlet pipes 9 and 11, gas outlet pipes 8 and 12 and a column packed with carbon material, said column being disposed between the melting bath 2 and outlet 7 and being heated by electrodes 10. The outlet disposed at the bottom of the chlorinator may be designed introduced into chlorinator 4 from above, for example, through inlet opening 11 or another opening disposed in melting bath 2 in order to avoid the formation of obstruc~ tions due to magnesium oxide in the upper part of chlori nator 4. When hydrogen chloride is used for chlorination, the off-gases also contain hydrogen. ~A charcoal ?lter heated for a short time to a tempera ture above the melting point of the salt should advan tageously be disposed in the off-gas outlet 12 of the chlo as over?ow. rinator so that escaping magnesium chloride vapors can 10 The following examples serve to illustrate the invention, be condensed. but they are not intended to limit it thereto: -It is known that magnesium chloride melts or melts of Example 1 salt mixtures containing magnesium chloride, which melts contain magnesium in the form of its oxide or carbonate, In continuous operation, 130 kg./h. salt containing can be treated with gaseous hydrogen chloride or phos 15 1.7% H20, 3.5% MgO, 7% MgSO.;, 2% KCl, 2.5% NaCl gene or chlorine and carbon monoxide. During this and MgClz (remainder) were introduced into melting treatment, the melt is allowed to trickle down in an elec bath 2. A magnesium chloride melt which was intensely trically heated trickling tower charged with lump coke, stirred by stirrer 3 had previously been introduced into which simultaneously serves as electrical resistance for the completely closed melting bath 2 so that the salt sup the electric current, and the reaction gases evolved in the 20 plied by charging device 1 was rapidly melted and depo trickling tower are conducted in upward direction. sition of magnesium oxide was avoided. The melt had a It is also known that the gases, such as chlorine or hy temperature of between 750° C. and 900° C. The melt drogen chloride, which ?ow in coutner-current to the was introduced through over?ow 5 into chlorinator 4 and salt melt, can be cycled. In this process, means are dis travelled to the electrically heated coke column through posed which serve to remove the water. :- which chlorine introduced via chlorine inlet 9 was passed All these known measures are partially employed in the in counter-current to the melt. In the lower part of chlo process of this invention. They constitute, however, par rinator 4 an anhydrous and sulfate-free melt which con tial steps which are combined with novel steps to result inha valuable new process. The process of this invention for the manufacture of an tained less than 0.1% MgO and about 95% MgCl2 (re mainder: alkali metal chlorides) was removed at 750° C.—850° C. by means of outlet 7. hydrous magnesium chloride substantially free from mag The oil-gases which consisted of HCl, C0, C02 and nesium oxide by chlorinating a salt which consists essen small amounts of C12 and S02 were removed in the upper part of chlorinator 4 by means of off-gas outlet 12,. tially of magnesium chloride containing from about ‘1—5% by weight water and from about 2—6% by weight magnesium oxide, the salt being introduced into a mag nesium chloride melt that is conveyed to a heated chlori nator, in which the ?nely distributed melt trickling down over carbon material is chlorinated with the aid of chlo rine, phosgene, a mixture of carbon monoxide and chlo rine, a chlorinated hydrocarbon or hydrogen chloride, the hydrogen chloride evolved by hydrolysis when the ‘salt is melted being used as additional chlorinating agent, corn 35 Example 2 The melting bath was charged in the manner described in Example 1 per hour with 110 kg. salt containing 4.3% H20, 5.6% MgO, 6% MgSOg 2% KCl, 2% NaCl (re mainder: MgClz). The melt which was intensely stirred in the melting bath 2 had a temperature of 800°~900° C. The melt was introduced through over?ow S into chlo~ rinator 4 where it was chlorinated in counter-current with chlorine. An anhydrous and sulfate-free melt which con prises introducing the magnesium chloride melt into a closed melting bath, advantageously disposed at a position tained 0.1% MgO and about 95.5% MgCl2 (remainder: above the chlorinator, intensely stirring said melt in said alkali metal chlorides) was removed at 750° C.—850° C. melting bath, introducing said melt in ?nely distributed through outlet 7. The o?~gases were removed through form through a central over?ow into the head of the chlo gas outlet 12. rinator, unmolten salt being removed at a position be We claim: tween the over?ow and the melting bath, whereby un 1. In the process for the manufacture of anhydrous molten salt is prevented from being entrained, and dis 50 magnesium chloride substantially free from magnesium charging an anhydrous magnesium chloride melt which is oxide by chlorinating a salt which consists essentially of substantially free from magnesium oxide at the bottom of magnesium chloride containing from about 1~5% by the chlorinator. weight water and from about 2—6% by weight magnesium The chlorinating gas which is used in counter-current oxide, the salt being introduced into a magnesium chlo~ is preheated to a temperature of about 750° C.—900° 0., ie the working temperature of the chlorinator. The oft’ gas escaping from the chlorinator may advantageously be ride melt that is conveyed to a heated chlorinator in which the ?nely distributed melt trickling down over carbonaceous ‘material is ‘chlorinated with the aid of at freed from magnesium chloride vapors by being passed least one substance selected from the group consisting'of through a heated charcoal ?lter which so to speak has chlorine, phosgene, a mixture of carbon monoxide and the function of a re?ux condenser. 60 chlorine, a chlorinated hydrocarbon and hydrogen chlo The hydrogen ‘chloride contained in the off-gas is again ride, the hydrogen chloride evolved by hydrolysis when used for chlorinating the melt. The hydrogen chloride the salt is melted being used as additional chlorinating which evolves in the melting bath during the reaction of agent, the improvement which comprises introducing the magnesium chloride with the water contained in the salt magnesium chloride melt into a closed melting bath dis powder, can be recovered from the cit-gas and used for posed at a position above the chlorinator, intensely stir chlorinating the melt. If the o?F-gas is removed at a posi ring said melt in said melting bath, introducing said tion approximately in the middle section of the chlorina melt continuously and steadily through a central over tor, the hydrogen chloride evolved during the reaction ?ow into the head of said chlorinator, intercepting any ?owsyif desired after admixture of a part of the total unmolten salt to prevent the same from being entrained as amount ‘of chlorine to be used, from the upper part of 70 the melt is introduced into said chlorinator, and dis the ‘chlorinator in co-current with the melt to the bottom charging an anhydrous magnesium chloride melt which ofp'said chlorinator and is thus used for chlorination. is substantially free from magnesium oxide at the bottom The apparatus used in carrying out the process of this of said chlorinator. invention ‘comprises a chlorinating tower 4, a melting 2. The process of claim 1, wherein the oft-gas escap bath 2 disposed at the upper end of said tower, a charg 75 ing from the chlorinator is freed from magnesium chloride 5 vapors by passing the gas through a charcoal ?lter heated to a temperature above the melting point of magnesium chloride. 3. The process of claim 1, wherein the oil-gas is re moved at a position approximately in the middle sec 6 between the vmelting bath and an outlet for removing the ?nal product at the lower end of the tower, electrodes connected with said column for heating the carbonaceous material, a gas outlet pipe at the middle of said column, another gas outlet pipe at the upper part of the column tion of the chlorinator and the hydrogen chloride evolved and a gas inlet pipe at the lower end of the column. is used in co-current for chlorinating the melt which References Cited in the ?le of this patent trickles down in the chlorinator. 4. An apparatus for the manufacture of anhydrous UNITED STATES PATENTS magnesium chloride which is substantially free from mag 10 579,039 Brashear ____________ __ Mar. 16, 1897 nesium oxide, comprising a chlorination tower, a closed 1,549,812 Siedler ______________ __ Aug. 18, 1925 melting bath disposed at the upper end of said tower, a charging device leading into said closed bath through which the salt mixture to be chlorinated is supplied, a stirrer extending into said bath, a central over?ow for 15 said bath, a gas inlet pipe leading into the top of the melting bath, an apron disposed between the melting bath and the overflow, a column Within said tower packed with carbonaceous material, said column ‘being disposed 1,702,301 1,999,179 2,355,367 laeger et a1. __________ __ Feb. 19, 1929 Burgess ______________ __ Apr. 30, 1935 Cooper _______________ _ Aug. 8, 1944 OTHER REFERENCES Serebryakova et al., “Chemical Abstracts," vol. 52, No. 17, pages 14992—3 (Sept. 10, 1958).